Hi! Here are a few changes you could try...
Put Life Orb and Roost on Hydreigon instead of Expert Belt and Sub. The added power allows Hydreigon's DM to be a real wallbreaking tool, and Roost helps mitigate LO damage and potential SR + sand damage too.
You also seems pretty Scizor weak. Th CB variant can get free switches against Gengar and Ferro and start wrecking shit. The SD set can find set-up chances against the same Pokemon and then procceed to OHKO your entire team, excpet for Starmie, which takes 61% min from +2 BP and is vulnerable to passive damage, Pursuit and frail, leaving Keldeo as your only check to it. My suggestion? Use Fire Punch over SR on Jirachi. This way you will be able to outspeed and OHKO Adamant offensive Scizor after SR and 1 LO round. You will also be able to hurt CB Scizor instead of being forced to take a huge amount of damage from U-turn. Fire Punch will also allow Jirachi to deal much better against Ferrothorn and Magnezone, which both seem problematic.
Finally, i suggest replacing Keldeo with Landorus-T. This is because Terrakion is a huge pain in the ass for this team, as is CB Scizor, which i mentioned earlier. LO Garchomp gets a kill every time he comes in if it predicts correctly too. Here is the set:
Landorus-T @ Leftovers
252 HP / 4 Atk / 252 Def
- Hidden Power Ice
- Stealth Rock
With Keldeo gone you are a bit more weak to Sheer Force Landorus, but Gengar can always revenge kill it, where Ferrothorn lives one hit and KOs back.
That was all i hope i helped, even though i am not so good at team rates.
Part of the OU QC team, message
me for a check!